Some remaining points:
* I didn't know what "@since version" I should put in the mli
* I didn't add i-equivalent functions for the deprecated ones in format
* I didn't add tests in tformat because the only one present was for the deprecated bprintf
* how should printf behave with malformed format ?

I've attached a new patch that contains more tests (ibprintf) (the former one can be deleted).
I did not add tests for the continuation printf because I don't know what to do.
Any suggestions would be welcome.